Leveling in v15.2 not prioritizing as expected

Using Leveling in v15.2, based on 2 Global Activity Codes and Total Float; it appears that the priority assigned to the predecessor activities is superseding the priority of the activity itself, even though the predecessor activity is not directly pushing the successor activity. Example: Activities A & B are competing for the same resource. Activity A has a higher priority than B.  If their predecessor priorities are the same then A is scheduled to happen first, but if B's predecessor is given a higher priority than A's predecessor then B is scheduled first, even though it has a lower priority